swift 1.13.0 delete account failed --504 Gateway timeout

I installed swift 1.13.0 (from source) in my test environment, in which there are 2 load-balancers, 2 proxy nodes and 5 storage nodes(running account-server, container-server and object-server).
I used swauth(1.8.0) as my auth service.

I can create accounts and users, and use those account&users to CRUD objects.
Everyting works well but, I just can't delete account!
I can delete a user, but when I execute swauth-delete-account -A URL -K swauthkey account_name,
it always reports Account deletion failed: 504 Gateway Time-out.
I also tried swauth 1.4.0, but encountered the same problem.
I don't know why, could someone help me?